1. Field of the Invention
The present invention relates to attenuation of fluid pressure pulses in hydraulic systems, and more particularly, to an apparatus for attenuation of fluid pressure pulses in a hydraulic system of an automatic transmission.
2. Discussion of Related Art
Many conventional automotive vehicles include an automatic transmission. Vehicle transmissions enable relatively wide variation in output torque as applied to the vehicle wheels while allowing the vehicle engine to operate within a relatively narrow range of engine speeds. Engine torque and speed are converted in the transmission in accordance with the tractive-power demand of the vehicle. A conventional transmission includes a hydromatic torque convertor to transfer engine torque from the engine crankshaft to a rotatable input member of the transmission through fluid-flow forces. The transmission then uses hydraulic pressure to automatically select the proper gears for the torque and speed requirements of the vehicle. A hydraulic pump is used to maintain proper hydraulic pressure within the transmission and to lubricate components within the transmission. The pump is typically contained within the transmission housing. The transmission fluid is cooled by routing the transmission fluid outside of the transmission housing to a transmission oil cooler that is typically mounted on the vehicle radiator. The transmission fluid is then returned to the transmission where it is redistributed by the pump.
The fluid pump in the transmission produces fluid pressure pulses during operation. These fluid pressure pulses create noise and energy surges at the pumping frequencies that relate to the pump speed. In particular, these pressure pulses produce audible noise, as well as structural vibration, that are transmitted into the vehicle structure. Developing a structure that is not sensitive to these pressure pulses may be time-consuming and costly and greatly affect design flexibility.
The inventors herein have recognized a need for an apparatus for attenuation of fluid pressure pulses in a hydraulic system of an automatic transmission that will minimize and/or eliminate the above-identified deficiencies.